The present invention relates to a seam for a multi-layer felt for use in a papermaking machine. The felts typically employed in a papermaking machine are manufactured either as a continuous loop or a flat woven felt. Often, papermaking felts are woven as a flat fabric which may be joined at two ends by a seam. Typical seams for a papermaker's felt comprise a plurality of spaced apart loops on each end of the felt to be joined which are mated in an intermeshing alternating relationship to form a substantially tubular channel through which a pintle is inserted in closing the seam.
As papermaking machines have developed, machine felt speeds of between 4000 and 5000 feet per minute have become common. Due to such high speeds, and resulting forces on the seam as well as the hostile conditions of temperature, pressure and environment to which such seams are exposed, seam durability is of concern. Also of concern, is the effect the seam design has upon the properties of the felt. For example, attempts to increase seam strength by increasing the diameter of the pintle requires increasing the diameter of the loops which results in an increased thickness for the felt in the seam area. Such increased thickness can result in imperfections in the product being produced as well as cause vibrations, due to imbalance, during running of the machine. Also, other properties of the felt, such as void volume which is directly related to the amount of water the felt can absorb, can be affected by such seams. This is of particular concern in felts used in wet press sections of a papermaking machine.
In the manufacture of certain paper grades such as pulp, corrugating medium and cylinder boards, sensitivity to seam marking is not a great concern. In such areas, the time necessary to install the fabric on the machine is of concern. For such applications the improved properties of a multi-layer felt are desired, however, the multiple pintle seams of such felts are undesirable due to the time involved in insertion of the pintles. In such areas, where seam marking is not a primary concern, multi-layer felts which are relatively easy to install have not previously been available.